Add native ESM entry points and runtime shims

[jasperan]

Summary

Addresses #93 by making the shipped debug_esm runtime self-contained enough for native ESM loading and by exposing representative package-level ESM subpath imports.

Problem

Oracle JET already shipped a debug_esm tree, but it was not directly usable under native ESM because:

• modules still used bare ojs/* specifiers
• parts of the runtime still assumed AMD-style resource loading
• package subpath imports like @oracle/oraclejet/ojkeyset were not exported
• parts of the older converter stack still referenced the wrong namespace alias under ESM
• theme-derived defaults could crash in non-browser hosts by touching window unconditionally

Changes

• rewrite debug_esm imports from bare ojs/* specifiers to relative ./*.js imports
• add dist/js/libs/oj/debug_esm/package.json with type: module
• add package-level exports so representative installed-package ESM subpath imports resolve cleanly
• replace AMD-plugin assumptions in config, locale, and timezone resource loading with a small runtime AMD-object loader that reads the already-shipped resource bundles
• fix legacy oj alias references in the older converter stack so number/date converters and date validators import cleanly under ESM
• guard theme-derived font-family parsing so non-browser hosts fall back cleanly instead of crashing

Verification

• direct-file ESM smoke passes for representative debug_esm imports
• installed-package Node ESM smoke checks pass across 20 representative imports covering utilities, data providers, converters, locale switching, validators, URL adapters, locale data, time utilities, and timezone utilities
• package smoke still passes with npm pack --dry-run

Scope / Caveats

• this PR focuses on making representative JET ESM entry points usable under native ESM without external aliasing
• the validation matrix is broad, but still representative rather than exhaustive for every possible entry in the package
• AMD debug and minified bundles are intentionally left untouched